The invention relates to a method, apparatus and computer program for embedding arbitrary information into contents and, more particularly, to a method, apparatus and computer program for embedding information into contents without degrading the contents.
Although techniques for embedding information into contents have been developed with respect to various contents (namely, digitized data) such as images, audio signal, text, drawings, and the like, an information embedding to an image will now be mentioned here as a typical example. Generally, for example, as disclosed in IBM System Journal, Vol. 35, No. 3 and 4, pages 313-336, 1996, according to the information embedding technique into an image, information is embedded by adding a slight change to a value such as an intensity or the like of a pixel.
There are the following requests from a viewpoint of the practical use with respect to such a value change.
(1) The change in value cannot be detected by the human sight (or, even if it can be detected, this does not become an obstacle of the image reference of the human being).
(2) Even if a process such as a JPEG compression or the like is performed to an image in which information has been embedded, the embedded information is not extinguished.
According to the conventional information embedding technique, as disclosed in the above literature, some devices have been made with respect to the kind of value as a target of the change in order to satisfy the requirement. That is, a change is added to the value so that the change is inconspicuous and is hard to be extinguished. For example, the image is expressed by a frequency value and a change is added to coefficients of middle-range values.
The relation between the change in value of the actual image and the change recognized by human sight differs every image and, further, depending on a region in the image. For example, although even a slight value change is conspicuous in a flat region, even a large change in value is inconspicuous in a jumble region such as a forest photograph.
According to the above conventional techniques, however, it is insufficient with respect to a point of optimizing a size of value change in dependence on the nature of the image. In case of giving a priority to the prevention of the visual change, therefore, it is necessary to reduce the value change by presuming a case of a flat image and a survivability to the image process is small. In case of giving a priority to the survivability to the image process, on the other hand, it is necessary to increase the value change and a visual change occurs in a flat image. That is, according to the conventional system, it is difficult to accomplish both of the prevention of the visual change and the improvement of the survivability to the image process.
It is an object of the invention to provide a method of embedding information into contents, wherein both of a prevention of a visual change and the improvement of a survivability to an image process can be accomplished and to provide a program to realize such a method and an apparatus for executing such method and computer program.
In the field of medical image processes, a 15 filter to make a diagnosis of a doctor easy for a human photograph photographed by using an X-ray or an MRI is being studied. The most advanced medical filter has the following nature as disclosed in the papers of The Institute of Electronics Information and Communication Engineers of Japan, D-II, Vol. J79-D-II, No. 8, pages 1347-1353.
(1) Noises are removed by a smoothing process.
(2) The shape is preserved with respect to edge information that is important to the human sight, namely, a portion where the nature of an outline or plane of an object changes and a point (singular point) where the color or brightness is particularly different as compared with that of the ambient portion.
When considering from another viewpoint, it is possible to consider that the medical filter has the following nature.
(1) The value of the image changes.
(2) The image does not visually change. Or, even if it changes, it does not become an obstacle of the human reference.
The above described problems are solved by using the features of the medical filter mentioned above. That is, the above problems can be solved by an information processing system having means for inputting contents and means for embedding information into the contents, wherein a value change of the contents which is imperceptible to the human being or which does not become an obstacle of the reference of the contents of the human being is performed by using the medical filter mentioned above, a region between the value before the change and the value after the change is set to a changeable range of the value in the information embedding, and the information is embedded by changing the value of the contents within the changeable range.